Unit 2 - Fibre Flashcards
What are fibre and board?
Types of packaging made from renewable plant-based resources such as cellulose fibres
Name the 9 most important properties of fibre packaging
- Dead fold
- Tensile strength
- Tear strength
- Porosity
- Stiffness
- Grease resistance
- Burst strength
- Printability
- Moisture absorbance
Describe dead fold
- Resistance to unfolding after creasing
- Important in box-making
- Dependent on fibre-orientation (CD>MD)
Describe tensile strength
Resistance to deformation in tension i.e. stretching
Describe tear strength
- Resistance to tearing
- Measured with Elmendorf tear test
Describe porosity
- Fraction of voids in the material
- Important in vacuum handling
Name the 10 types of paper
- Kraft
- Test
- Chip
- Newsprint
- Printing and writing
- Tissue
- Label
- Greaseproof
- Glassine
- Parchment
Describe Kraft paper
- Strongest of all papers
- Can be machine-glazed and calendered for smoothness
- Typically brown but can be bleached (white)
Describe test paper
- Pale brown - paler than Kraft
- Less strong than Kraft
- Contains recycled fibres
- Can be single or double play
Describe chip paper
- Very high recycled content
- Grey in colour
- Weakest of the papers
Describe newsprint paper
- 70% recycled pulp and 30% filler
- Designed for speed and ink absorbance
Describe printing and writing paper
- Varying thickness
- Often coated for photos
- Photocopying paper is designed to withstand heat with minimum curl and controlled electrostatic properties
Describe tissue paper
- Generic term for any lightweight paper e.g. toilet tissue and kitchen roll
- Balance between absorbency and wet strength
Describe label paper
- Grade is determined by print quality
- Most are coated on one or both sides
Describe greaseproof paper
- Pulp is chemically treated and highly beaten
- Fine fibres for reduced absorption
- Sometimes coated
Describe glassine paper
Is extremely greaseproof and supercalendered for smoothness
Describe parchment paper
Acid-treated and small fibres
Name the 4 types of board
- SBB - solid bleached board
- SUB - solid unbleached board
- FBB - folding box board
- WLC - white lined chipboard
Describe solid bleached board
- 100% bleached chemical pulp
- Clay / pigment coated to improve brightness
- Used for aroma-sensitive products
- C2S - coated on both sides
- Used widely in USA
- Develops intentional creases easily
Describe solid unbleached board
- Clay / pigment coated
- Unbleached chemical pulp
- Used for folding cartons or liquid packaging
Describe folding box board
- Layers of mechanical pulp between layers of chemical pulp
- C2S - coated top and bottom
- Low density and high stiffness
- Less crease performance
Describe white lined chipboard
- Sometimes called recovered fibre carton board or coated recycled board
- Coating on the outer layer for printability
- Centre is recycled fibre but outer is bleached chemical pulp
- Dense but low strength
Name the 13 factors affecting fibre packaging performance
- Fibre aligment
- Moisture content
- Grammage and thickness
- Tensile strength
- Tear strength
- Folding resistance / stiffness
- Water absorption
- Porosity
- Burst strength
- Printability
- Surface strength
- Surface tension
- Rub resistance
Describe how fibre aligment affects: tensile strength, tear strength, folding resistance, and stiffness
- Tendency for fibres to align in the direction of travel of the moving belt - this gives the MD and CD which is the ‘grain’ of the paper
- Tensile strength is greater in MD as it is more difficult to break fibres along their length
- Tear strength is greater in CD as it is easier to tear between fibres than across them
- Folding resistance is greater in CD as you are folding across fibres
- Stiffness is greater in MD
Describe how moisture content affects fibre packaging performance
- Cellulose fibres absorb moisture and swell as they are hygroscopic: therefore, testing should be carried out after sample conditioning (23°C at 50% RH)
- Change in the moisture content will affect the dimensions, the stiffness, the strength, and flatness
- Fibres swell across the width and increase in size in the cross direction
- Coatings can give an exaggerated effect as the moisture is preferentially absorbed into the uncoated side of the paper
Describe tensile strength and how it affects performance of fibre packaging
- Tensile (pulling force) required to produce a rupture in a strip of paper
- Measured in both MD and CD and is measured in kN/m
- Indicative of fibre strength, fibre bonding, and fibre length
Describe tear strength and how it affects performance of fibre packaging
- Indicates behaviour of paper in various end-use situations such as web-runability, toughness, and the ability to absorb shocks
- Important factors are fibre length and inter-fibre bonding
- Longer fibres improve tear strength as the fibres can distribute stress better
- Measured in both MD and CD and is expressed in mN
Describe folding resistance / stiffness and how it affects fibre packaging performance
- Measure of force required to bend paper / board through a specified angle - this is a measure of flexural rigidity
- Stiffness is defined as the bending moment (g-cm) needed to deflect the free end of a 1.5in wide vertically clamped sample 15° from its centre line when load is applied 50mm away from the clamp
- Measured in MD and CD
Describe water aborption and how it affects fibre packaging perfomance
- Done via Cobb test to determine water absorption over 60 seconds and is expressed in g/m^2
- Can effect the strength and propensity to curl
- Results are dependent on water temperature so a standard of 23°C is used
Describe porosity and how it affects fibre packaging performance
- Measured using the Gurley method and is defined as the resistance to the passage of air when a pressure difference exists between the 2 sides
- The time for a given volume of air to flow
- Air resistance is an indirect indicator of degree of pulp beating, fibre compaction, and the amount of filler used in the production process
- Vital when vacuum handling is used
Describe burst strength and how it is measured
- How much pressure a paper can tolerate before it ruptures
- Measured as the maximum hydrostatic pressure required to rupture the sample by constantly increasing the pressure applied through a rubber diaphragm on a 1.2in diameter samples
What 6 things affect fibre packaging printability?
- Surface smoothess
- Surface strength
- Surface absorption
- Surface tension
- Whiteness
- Opacity
Describe surface strength and how it is measured
- Also called the wax pick test and is a measure of the surface strength (or resistance to picking)
- Picking occurs due to the poor internal bonding strength
- Tested using a series of graded wax sticks (Dennison test) - when the wax has set, it is peeled off and the degree of fibre adhesion to the cold wax in measured (only for uncoated samples)
- An acceptable pick level is #6
- For coated grades, the IGT pick test is used, where a tacky ink is applied and moved at an increasing speed
- An acceptable IGT is >300
Describe surface tension
Affects how ink ‘wets out’ on the paper surface
Describe rub resistance
Determines how resistant a paper is to losing printed inks
Describe the three types of fibre used in papermaking
- Paper is made from cellulose wood fibres - mostly from north European softwood trees
- Virgin hardwoods: most common species are birch and eucalyptus; they have short fibres which helps to give a smooth surface
- Virgin softwoods: from coniferous trees such as pine and spruce; have long fibres which give high strength due to the greater surface area and fibrillation of fibres; however, if they are used on their own then they would produce a sheet with poor smoothness and poor printability
- Recycled fibres are also used (which will have clays and calcium carbonate in)
- Every time a fibre is recycled, it gets shorter resulting in a paper with higher density, lower bulk, and weaker physical strength
Name the 5 steps of fibre extraction
1.Logging / debarking
2. Pulping
3. Refining
4. Bleaching
5. Final preparation
Describe logging and debarking during the fibre extraction process
- Trees are harvested and transported to a pulp mill where they are de-barked
- Bark is used as fuel (known as hog fuel)
- Logs are reduced to chips
Describe mechanical pulping
- Only produced from softwood pulps
- Physical grinding of wood chips to form a slurry with water
- Softens the lignin but does not remove it - this residual lignin actually increases strength of the paper
- It is a fast method and is used for low-grade paper
- Type 1: thermo-mechanical (TCP)
- Used in integrated mills
- Uses 2+ rotating discs with bars machined into the surface
- The distance between the discs is adjusted to make the correct pulp quality
- The discs rotate in opposite directions which grinds the woodchips into fibres - this is called fibrillation
- Called thermo-mechanical because a lot of heat is generated as steam which is used to soften the chips
- Produces pulp with better bulk and strength properties
- Type 2: chemi-thermo-mechanical pulp (CTMP)
- Same as TCP but with chemicals added, such as sodium metabisulphite, to improve brightness of the pulp
Describe chemical pulping
- Digestion of wood chips with chemicals and temperatures of 160°C
- Process dissolves and removes 95% of the lignin and does not shorten fibres
- More expensive and slower than mechanical pulping, but gives a strong final paper
- Type 1: elemental chlorine-free (ECF)
- Uses chlorine dioxide and ozone in a multi-stage bleaching process
- Type 2: totally chlorine-free (TCF)
- Also multi-stage but only uses ozone
- The Kraft process is used to cook the fibres and separate them - this produces an unbleached pulp
- Produces longest and strongest fibres
Why was a new method of pulp bleaching developed?
Developed in response to ban of elemental chlorine bleaching - dioxins and furans produced are linked to cancers
Name the 7 additives that can be added to fibre pulp
- Size
- Starch
- Bactericides
- De-foaming agents
- Colours
- OBA - optical brightening agents
- Fillers
Describe size additives
- Controls water absorption and ink penetration
- When added at the wet end, it is an emulsion of rosins
- When added at the dry end as a surface application, it is mostly a polyurethane and starch emulsion
Describe starch additives
- When added at the wet end, it is used to improve the internal ply-bond strength (in the z-direction)
- Usually in the form of Farina (potato starch)
- Ply-bond strength is important as a good carton crease relies on partial delamination of the internal plies
- When applied at the dry end, it can improve printability in uncoated grades and reduce linting - usually maize starch
Describe bactericide additives
- Used at the wet end as temperatures are high in paper mills which can lead to bacteria growth - starch also contributes to this
- Starch makes bacteria grow which is not good for food contact and can cause runability problems
- Bromine is used to instantly kill bacteria and no residual is left in the water
Describe de-foaming agent additives
- Usually a silicone emulsion - traditionally mineral oils or paraffin
- Needed as air bubbles can disturb formation or lead to ‘skips’ in coatings
At which stage are paper colours added?
Wet end
Describe OBA additives
- Complex and very expensive alternative to fluorescent whitening agents (FWA)
- Used in the wet end or as a coating
Describe filler additives used in papermaking and give three examples
- Added to reduce cost and give properties such as printability, brightness, opacity, and dimensional stability
- They fill the interstices of the paper to give a smooth finish and greater ink receptiveness
- They interfere with fibre bonding, giving a softer feel, but reducing strength
- Usually China clay (Kaolin), chalk, and titanium dioxide
Describe the differences between an integrated and a non-integrated paper mill
- In an integrated mill, pulp is transferred directly to the papermaking machine
- In a non-integrated mill, pulp arrives in the form of sheets which are then mixed with water in a machine called a hydrapulper
Describe the refining process of fibre extraction
- A mechanical process which bruises and splits fibres to increase their flexibility - this is called fibrillation which increases the surface area of the fibres and controls fibre length distribution
- Primary refining is done in a disc refiner then secondary refining is done in a conical refiner
- The higher surface area means more hydrogen bonds can form and give more interlocking
- A better fibre length distribution means better uniformity and printability
- Fibres can be put through a fractionator so only fibres of the correct length are used
How are fibres bleached?
If the paper needs to be white, the pulp is bleached with chlorine-containing compounds or hydrogen peroxide
Describe the final preparation processes for fibre extration
- Additives are put into the pulp (now called Furnish)
- Sizing agents such as rosins to control water and ink absorption
- Starches and gums for burst and tensile strength, stiffness, and pick resistance
- Clay and chalk for brightness and better printability
- Pulp then goes through screening to ensure there are no contaminants
- Then diluted to reach the required consistency
- > 1% for paper
- 0.2 - 0.2% for board
List the processes in a Fourdrinier machine
- Wet end
- Head box
- Slice lip
- Wire (also called Fourdrinier table)
- Press - Dry end
- Heated cylinders / air dryers
-Surface finishing processes
How is pulp supplied to a Fourdrinier machine?
Paper pulp with 97-99% water content onto a moving belt where water is drained
How many layers can a Fourdrinier machine made?
1
Describe a Fourdrinier forming wire
The forming wire is a continuous loop of plastic mesh which acts as a sieve to allow water to drain which leaves an even layer of fibres on the surface
What is the purpose of a headbox in a Fourdrinier machine?
The headbox ensures sufficient turbulence in the thin stock so that it is evenly dispersed and delivered at an even pressure to the slice across the full width of the machine
What is the purpose of a slice in a Fourdrinier machine?
The slice is used to control the size of a slot band and is divided into many sections, each about 20cm wide
Describe how water is removed on a Fourdrinier wire
- On the wire, water is removed by a combination of gravity and creating a pressure differential using table rolls on slower machine and high speed foils on faster machines - the foils create a downdraft to help draw water down
- You know all water has been removed when you can see a dry-line across the sheet
What is the purpose of a Fourdrinier couch roll, and what is the water content of the paper at this stage?
Picks up the sheet onto a continuous felt belt
75%
Describe secondary pressing in a Fourdrinier press and the water content of the paper at this stage
- The sheet then continues to the secondary pressing where the water content is now low enough that it can no longer be suctioned out; water must be squeezed into the felt belts by hydraulic rolls - at this point, only one felt is used
- The water content is now approximately 50%
Describe the drying cylinder process in a Fourdrinier machine
- Next is the drying cylinders which is the most energy-intensive and costly part of the process
- Sheet passes through many drying rolls to reduce the moisture content to 8%
- On some machines, there is an MG cylinder between the drying cylinders which are up to 5m wide and have a highly-polished surface
- Sometimes also sizing press in the middle which applied a size solution to control picking and water absorption
Describe the final coating station of a Fourdrinier machine
- Some machines have a final coating station to apply a pigmented coating for good printability
- Usually water-based so are dried using a combination of infra-red and hot air units
Describe how a calendering unit works on a Fourdrinier machine
- May also be a calendering unit which helps to smooth the paper and ensure an even thickness across the web
- Pressure of 700kg/cm^2 and 300°C
- Smoothness is caused by a differential speed difference
What is a cylinder / vat machine used to make?
Thicker board
Describe the old method of a cylinder / vat machine
- A series of cylinders that each have a forming wire and a vat containing dilute paper stock
- The wet sheet forms on the cylinder as it comes out of the vat and it couched off onto a felt belt on the underneath - this happens at every vat, each ones adding roughly 30gsm over 8-10 vats
Name the new method of a cylinder / vat machine and describe how it works
Inverform
- Designed due to speed limitations
- The formers are inverted so each layer is put on top of the previous one
- This is used in all modern machines
Describe a twin-wire Fourdrinier machine
- Two sheets are formed separately then bought together in their wet state
- There is a top and bottom felt to help drain water
- As fibres are layered down, there is less fibre bonding than Fourdrinier
What are reels called when they still have the deckle edges?
Pope reels
Describe how paper is slit at the end of a papermaking machine
- Slit to customer widths with as little waste as possible
- Uses two circular knives which are at the top and bottom
- The top knives are sacrificial and act in a scissor action
- A bad quality slit can cause fibrous debris
- Rewind is formed of rollers which each run faster than the last to ensure the sheet remains taught
Describe how paper is sheeted at the end of a papermaking machine
- For carton production, most printing presses are sheet-fed lithography
- The cutting heads use two rotary knives which cut in a scissor action
- Cut sheets are carried down the machine by tapes running over rollers to the delivery ‘lay-boy’ where they are placed on a pallet
Name 3 on-line quality checks done during papermaking
- GSM
- Thickness
- Moisture content
Name 3 off-line quality checks done during papermaking
- Inter-ply bond strength
- Cobb
- Smoothness
Name the 3 processes used to make a folded carton from a sheet
- Printing and decoration
- Cutting and creasing
- Gluing
What must happen to a sheet of board before it is made into a folded carton?
Stored under controlled conditions and allowed to stand for 48 hours to acclimatise
What printing method is used for a folded carton?
Offet lithography
Describe how folded cartons are cut and creased
- The printed sheet is cut and creased to the shape of the carton blank using a flat die or rotary cutting dies
- Sharp knives produce cuts
- Blunt knives produce creases
Describe embossing of a folded carton
- Embossing can be carried out during the die-cutting process
- Achieved by shallow knives
- Either aesthetic or functional such as braille
Describe foil blocking of a folded carton
- Foil blocking is only for decoration
- Foil is fed in on a carrier layer which is then peeled away to leave the foil attached to the board
Describe the gluing process of a folded carton
- Cartons are typically glues down the vertical side seam (straight line gluing)
- May also be glued at the base for easier construction (glued crash locks)
- They are pressed between 2 blankets to ensure the adhesive has bonded
- The major creases are usually folded through 160° to ensure they don’t resist carton erection
Name the two types of carded display packaging
- Blister packs
- Carded skin packs
Describe a blister pack
- Composed of a rigid, thermoformed plastic shape which is attached to a paperboard backing card - they usually are adhesive bonded together
- The backing card can be perforated to give a convenient opening feature
- Sliding designs provide repeat and easy access to the product and require no heat-sealable coatings
Name the 6 important properties of a plastic used for a blister pack
- Cost
- Mouldability
- Impact resistance
- Scuff resistance
- Low-temperature
- Clarity
Name 3 plastics used in a blister pack, why, and a disadvantage
- PVC (polyvinyl chloride) performance varies depending on the formulation
- Compatibility with adhesives should be evaluated
- Can have a slight blue or yellow cast
- Require low temperature performance
- PET (polyethylene terephthalate) is fairly cost-effective and offers superior performance
- Polystyrenes have excellent clarity but low impact resistance unless a special high-impact grade is used
How thick are plastics when used in a blister pack?
Majority are 0.12-0.18mm in thickness
How thick is the board used in a blister pack, and what does it depend on?
- Board must be selected according to the weight of the product being packed
- Usually between 500-800µm in thickness
- Suitable thickness can be achieved by doubling a lighter sheet - this is particularly useful for reinforcing pegboard holes
What does board used for blister packs NOT require?
Most blister packs are flat and do not require the board to have good folding properties
Give 4 properties that board must have in order to be used as board for blister packs and why
- Receptive to print
- Good internal bond strength to resist ply separation
- Porous so a vacuum can draw through the board to create the conforming skin
- Stiff so it doesn’t curl or delaminate
How is a plastic applied to board for a blister pack?
- After printing, the board is coated with a heat-sealable top coat and the blister is attached by the application of heat
- Printing inks must be able to withstand the temperature
- A properly-sealed pack will show fibre tear
What type of board is used for the following blister pack applications:
1. Hardware applications
2. When the back will be printed
3. When a high-quality appearance is needed
- Coated chipboard
- Double white-lined stock
- Solid bleached board
Describe how a carded skin pack is made
- Made by placing the product on a flat board sheet, then draping a heated plastic film over it
- A vacuum is created to draw the film down around the product and a heat-activated adhesive bonds to the board
Give three advantages of using a carded skin pack
- They are more economical than blister packs as no special tooling is required - the product is the mould
- Process is also easily adapted to small or large runs
- It also immobilises the packaging for security
Name the 2 prorietary gable top containers and their primary uses
TetraPak and Combibloc
Milk and fruit juice
Describe a gable top container
- Usually tube-style cartons made from polyethylene-coated board
- The coating is heated on the filling line to seal the pack
Describe a spirally-wound can
- Usually made from 3 overlapping spiral winds of recycled paper overlayed with bleached or natural Kraft paper
- Inner wind can be laminated with foil or polyethylene to provide a barrier and liquid resistance
- Usually have a round body but it is possible to make them rectangular
Describe a convolute can
- Made by rolling a rectangle of paper to the desired number of layers
- Bodies can be round, oval, or oblong and are difficult to make watertight, so most are for dry products
- Containers are formed by printing a flat blank, then forming the shape around a mandrel using glue to form an overlap seal, then the ends are beaded and the end is added
What 3 materials can be used for the end of a spirally-round or convolute can
Paperboard, metal, or plastic
What is the main function of moulded pulp?
Cushioning (especially for small electrical goods)
Give three characteristics of moulded pulp
- Produced from waste paper
- Can be coloured for aesthetic effect
- Can be waxed for moisture resistance
Name the 3 stages of moulded pulp production and describe them
- Stock preparation
- The pulper combines pulp and water to provide stock of approximately 4% solids - 1% of these are resins which help bind the final pack together
- Colour may be added as required
- Wet forming section (rotary)
- A forming die is immersed in a vat of stock and a vacuum system attracts fibre into the screen of the die; water is drawn away through the die, leaving a shaped pulp product
- Drying section
- Transferred to the drying section when it contains 75% water
- Recycling hot air drying is used to reduce moisture content to approximately 8%
When are rigid boxes used?
They are used when high-quality is required and good rigidity is needed for product protection
Describe the construction of a rigid box
- Made from board and cover pages
- Board is cut and creased with a score wheel
- The base and lid are made and the corners stayed - this means reinforced
- Pre-cut paper is used to cover the lid and base
Give an advantage of rigid boxes
Re-used for long-term storage such as jigsaws
Give 3 disadvantages of rigid boxes
- Not suited to high-speed production
- Manufacture is labour-intensive
- Expensive
How are backs and sacks made from, and how much weight can they hold?
Kraft paper in a reel-fed process using semi-extensible paper, and can hold up to 32kg
Describe 2-ply bag manufacture
- The inner tube is formed and the side-seam is glued
- The outer tube is formed around the inner tube, then the seam is glued and both tubes are attached to each other
- This multi-wall tube is cut, and the bottom is folded and glued
Describe multi-wall paper sack manufacture
- Produced by running 1-4 plies of paper together to form a tube
- The paper is off-set slightly so each ply bonds separately when adhesive is applied
Name and describe the 6 types of paper sack
- Self-opening sack - with our without paper handles
- Sewn and open-mouth - with our without plastic handles
- Roll-bottom - for pet food and granular products
- Pinch-bottom - bottom is rolled twice to give a sift-proof bottom for powder products
- Block bottom - gusseted and allows sack to stand up on the shelf
- Valve sacks - for chemicals and fine powders
Describe the formation of corrugate and name the four main material types
- Consists of a layer of fluted paper (roughly 105gsm) sandwiched between 2 layers of paper (roughly 125gsm each)
- This gives high strength but using less materials
- Accounts for 56% of fibre packaging in the UK
- Formed of four main material categories: Kraft, test, chip, and fluting
Name and describe the 5 types of Kraft paper used in corrugate manufacture
- Brown Kraft is naturally brown in appearance and the shade can vary depending on mill location, fibre source, and the pulping process
- White top Kraft was developed to have a good appearance with high strength but at a lower cost than traditional bleached Kraft; there are two main types:
- White top liner - a top skin of bleached fibres on a natural fibre base
- Coated white Kraft - a white coating (usually Kaolin) on a white top kraft or bleached fibre base
- White mottled Kraft (sometimes called oyster) is made in the same process as white top liners but the skin of white is randomly distributed to give a mottled appearance
- Bleached Kraft has slightly less strength but are rarely used nowadays
- Birch-faced Kraft is where the top ply is made from birch fibres which are bleached using oxygen
Name and describe the 3 types of test liner used in corrugate manufacture
-
Test liner 1
- Predominantly recycled fibres
- Have a Ring Crush Test value similar to Kraft paper
- Most often used as inner liners
-
Test liner 2
- Predominantly recycled fibres
- Have a RCT value that is 90% of that of Kraft
-
Test liner 3
- Predominantly recycled fibres
- Have a RCT value that is 75% of that of Kraft
- Vary in colour and appearance from one source to another
- Sometimes dyed and most often used as inner liners
Describe chip used for corrugate manufacture
- Manufactured from recycled fibres and are usually unsized
- Used as inner or centre liners
- Usually dyed brown or undyed grey
- Can also be called ‘container middles’
Name and describe the two categories of fluting used in corrugate manufacture
- Recycled fluting
- Made from 100% recycled fibre and usually sized
- Semi-chemical fluting
- Manufactured from hardwood pulp with some softwood and recycled fibres
- Used for heavy-duty packaging and high humidity conditions
Describe the frequency of fluting
How many peaks per length of board
Describe the amplitude of fluting
How high the peaks are
What is A fluting used for?
A fluting is mostly used in the USA for applications requiring high impact strength e.g. refrigerator packaging
What are C and B fluting used for?
C and B fluting is used for some transit packaging or display packaging for canned goods
Which flutes give the best print quality?
E and F
Describe the process of making corrugate
- Paper is first conditioned to ensure the correct moisture content to prevent bowing and curling which could jam machinery
- Flutes are formed using the ridges of the corrugator rolls with steam and pressure
- Following this, a starch adhesive is applied to the tips and combined with a liner to produce a single-face corrugate
- This is repeated until the desired wall type is achieved
- Anything more than a single-face cannot be coiled and so is slit into sheets for carton blanks to be cut from
Define a regular slotted case
A case in which all cuts and scores are in straight lines - these require no special tooling
In a regular slotted case, which direction do flutes go for maximum vertical compression strength?
Vertically
Describe a FEFCO 0201 regular slotted case
- Long side flaps meet in the centre of the box
- Uses the minimum amount of board in its construction
Describe a FEFCO 0203 regular slotted case
- Long side flaps totally overlap
- Provides additional protection but uses more material
Describe a FEFCO 0204 regular slotted case
- Both axis flaps meet in the middle of the box
- Good protection for the product
- Requires extra tooling to die-cut the short side panels which increases the cost of production
Describe a die cut case
Any case with angled or curved creases or cut-outs requires die-cutting
Name and describe the two types of dies used in die cutting cases
- Flat bed die
- All knives and blunt strips are laid out on a flat blank
- Rotary die
- A curved die that is wrapped around a cylinder
Give 2 advantages and a disadvantage of die cut cases compared to regular slotted cases
- Advantages
- More complex designs
- Dimensionally more accurate
- Disadvantages
- Higher cost as each design needs a separate die
Why must knives used for cutting cases be sharp
?
- Cutting knives must remain sharp otherwise you get swarf - this are bits of corrugate that are left attached
- This will fall into the machine and jam it
What is 3-point scoring used for and how thick is it?
3-point scoring uses a 1.1mm thick rule and is used for B, E, and smaller flutes
What is 5-point scoring used for and how thick is it?
5-point scoring uses a 1.5mm thick rule and is used for A, C and double-wall corrugates
What 3 printing processes are usually used for cases?
Include flexographic, screen, and offset lithography
Give a disadvantage of pre-printing cases
A lot of redundant stock if the design needs to be changed
Describe how cases are assembled
- After cutting, the cases are usually pre-folded and glued (usually the side joint)
- Other conversion may include stitching (stapling) or taping to assemble the joints
- Produces the most secure closure and is used for heavy-duty transit cases
- As this method uses metal, it is not food contact approved and cannot be used for food products
Name 10 performance properties of corrugate cases
- Viscoelasticity
- Moisture resistance
- Mullen burst strength
- Edgewise compression strength
- Flat crush test
- Porosity
- Surface friction
- Glue seam strength
- Print quality / print adhesion
- Product resistance
Describe viscoelasticity of corrugate
Corrugate is manufactured using tension and pressure which will revert to its original state over time (the crease will reduce in quality)
Describe how moisture resistance of corrugate can be increased and why it is needed
- An increase in moisture content quickly reduces the compression resistance
- For each 1% increase in moisture content, the compression resistance falls by 10-15%
- Treatments can either be in the paper itself or applied as a coating
- Thermoset resins and waxes can provide wet strength
Describe how Mullen burst strength is tested for corrugate
Uniform force is applied and is recorded when the liner fails
What is edgewise compression affected by for corrugate?
Fluting style
Describe flat crush test for corrugate
- Performance in printing and assembly machines
- Measures resistance of fluting to failure
- Is called the Concora test when done on fluting alone
Describe porosity testing for corrugate and in what instance it is critical
- Often called Gurlen porosity test and measures airflow though corrugated material
- Critical for vacuum handling systems
Why is surface friction important for corrugate?
Relates to food stability on pallets
